Flat steel strands are continuously cast on casting lines in oscillating molds which have generally rectangularly shaped cavities defined by two opposed pairs of general vertical side walls. Liquid metal from upstream steel-making operations is poured into a mold through a pouring nozzle of an overhead tundish. The tundish pouring nozzle typically extends through a protective slag cover and into the underlying liquid metal in the mold cavity for introducing the liquid metal with low turbulence in order to minimize splashing or entraining slag. Also, the pouring nozzle must be sufficiently spaced from the mold side walls in order to not to interfere with the formation of a strand skin having smooth surface and low transverse stresses.
The rate at which a thin flat metal strand, having a thickness of about 75 mm. or less, can be cast is limited to the maximum rate at which liquid metal can be poured into the mold cavity without substantially affecting the formation of the strand skin. Various specially designed tundish pouring nozzles and mold configurations have been developed for introducing liquid metal at high rates into the mold cavities. U.S. Pat. No. 4,811,779 discloses a design where a fan-shaped nozzle is submerged in a mold cavity for casting thin strip. Another design provides a funnel-shaped nozzle which extends between generally parallel side walls of a mold. While such narrow nozzles effectively distribute liquid metal in the mold cavity, they also tend to introduce turbulence in the metal which may interfere with the formation of a suitable strand skin. Also, narrowed nozzles are frequently sensitive to plugging because of the disposition of refractory particles, such as aluminum oxides, which may upset the entry conditions into the mold cavity.